http://recipes.alliantpowder.com/index2.html
Check out the Cowboy data and you'll find loads for the .44Mag that are at the same level as the .44Special in the regular section. I use a modest charge of 2400 under a swaged lead 240 gr Hornady bullet(softer than cast) w/no leading. I had the same leading problems using Unique. My guess was the Unique burned faster/hotter and was melting the base of the bullet. I get more velocity out of the 2400 w/no leading.